Also a video explaining this : <a href="https://www.youtube.com/watch?v=QCq9Xoo1EXk">https://www.youtube.com/watch?v=QCq9Xoo1EXk</a>
<pre class="shiki github-dark shaku"><code>/** * @param { string[][] } message * @returns { string } */function decode(message) { if (message.length === 0) return '' if (message[0].length === 0) return '' const rows = message.length const cols = message[0].length let result = '' let row = 0 let col = 0 let directionY = 1 while (col &lt; cols &amp;&amp; row &gt; -1 &amp;&amp; row &lt; rows) { result += message[row][col] col += 1 row += directionY if (row &gt; rows - 1) { directionY = -1 row -= 2 } else if (row &lt; 0) { directionY = 1 row += 2 } } return result}</code></pre>